core/misc/drupal.js                      |  2 +-
 core/modules/locale/locale.libraries.yml |  9 +++++++++
 core/modules/locale/locale.module        | 29 ++++++++++++++++++++++++++---
 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/core/misc/drupal.js b/core/misc/drupal.js
index 4244ed6..bbb05c0 100644
--- a/core/misc/drupal.js
+++ b/core/misc/drupal.js
@@ -1,7 +1,7 @@
 /**
  * Base framework for Drupal-specific JavaScript, behaviors, and settings.
  */
-window.Drupal = {behaviors: {}, locale: {}};
+window.Drupal = {behaviors: {}, locale: window.drupalTranslations || {}};
 
 // Class indicating that JS is enabled; used for styling purpose.
 document.documentElement.className += ' js';
diff --git a/core/modules/locale/locale.libraries.yml b/core/modules/locale/locale.libraries.yml
index 69efb02..de92ebc 100644
--- a/core/modules/locale/locale.libraries.yml
+++ b/core/modules/locale/locale.libraries.yml
@@ -18,3 +18,12 @@ drupal.locale.datepicker:
     - core/jquery
     - core/drupal
     - core/drupalSettings
+
+translations:
+  # No sensible version can be specified, since the translations may change at
+  # any time.
+  js:
+    # This file does not actually exist; it's a placeholder file that will be
+    # overriden by locale_js_alter(), to use the file that contains the actual
+    # translations, for the language used in the current request.
+    locale.translation.js: {}
diff --git a/core/modules/locale/locale.module b/core/modules/locale/locale.module
index 0b07f54..6e9f9c1 100644
--- a/core/modules/locale/locale.module
+++ b/core/modules/locale/locale.module
@@ -447,14 +447,28 @@ function locale_cache_flush() {
  * Implements hook_js_alter().
  */
 function locale_js_alter(&$javascript, AttachedAssetsInterface $assets) {
+  // @todo remove this in https://www.drupal.org/node/2421323
   $files = array();
   foreach ($javascript as $item) {
     if (isset($item['type']) && $item['type'] == 'file') {
+      // Ignore the JS translation placeholder file.
+      if ($item['data'] === 'core/modules/locale/locale.translation.js') {
+        continue;
+      }
       $files[] = $item['data'];
     }
   }
-  if ($translation_file = locale_js_translate($files)) {
-    $javascript[$translation_file] = drupal_js_defaults($translation_file);
+
+  // Replace the placeholder file with the actual JS translation file.
+  $placeholder_file = 'core/modules/locale/locale.translation.js';
+  if (isset($javascript[$placeholder_file])) {
+    if ($translation_file = locale_js_translate($files)) {
+      $js_translation_asset = &$javascript[$placeholder_file];
+      $js_translation_asset['data'] = $translation_file;
+      // @todo Remove this when https://www.drupal.org/node/1945262 lands.
+      // Decrease the weight so that the translation file is loaded first.
+      $js_translation_asset['weight'] = $javascript['core/misc/drupal.js']['weight'] - 0.001;
+    }
   }
 }
 
@@ -537,6 +551,15 @@ function locale_library_info_alter(array &$libraries, $module) {
       'firstDay' => NULL,
     ];
   }
+
+  // When the locale module is enabled, we update the core/drupal library to
+  // have a dependency on the locale/translations library, which provides
+  // window.drupalTranslations, containing the translations for all strings in
+  // JavaScript assets in the current language.
+  // @see locale_js_alter()
+  if ($module === 'core' && isset($libraries['drupal'])) {
+    $libraries['drupal']['dependencies'][] = 'locale/translations';
+  }
 }
 
 /**
@@ -1203,7 +1226,7 @@ function _locale_rebuild_js($langcode = NULL) {
       $data['pluralFormula'] = $locale_plurals[$language->getId()]['formula'];
     }
 
-    $data = 'Drupal.locale = ' . Json::encode($data) . ';';
+    $data = 'window.drupalTranslations = ' . Json::encode($data) . ';';
     $data_hash = Crypt::hashBase64($data);
   }